Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-1



# 6 Air Quality Impact Assessment On July 23, 2012, ENVIRON International Corporation (ENVIRON) submitted to EPA Region IV and the U.S. Fish and Wildlife Service (FWS) an Air Quality Analysis Modeling Protocol for the StatOil Gulf Services, LLC (Statoil) OCS Permitting Project (OCS Project). ENVIRON responded to EPA and FWS comments on the protocol (telephone conversation with EPA’s Stan Krivo on August 23, 2012; and via email from FWS on July 30, 2012). ENVIRON followed the protocol, with the FLM/EPA requested changes/additions, in performing this air quality impact assessment. The original PSD application was received by EPA on September 10, 2012 As documented in Section 4.1 of the original PSD permit application, the pollutants subject to Prevention of Significant Deterioration (PSD) review for the proposed Statoil exploration activities are NO X 

### and PM 2.5 

### . Direct PM 2.5 

### emissions did not trigger PSD review, but emissions of a PM 2.5 

### precursor (NO X 

### ) is subject to PSD review. The original PSD application was deemed incomplete on October 10, 2012. ENVIRON responded with additional information requested by EPA on December 10, 2012; January 30, 2013; and April 25, 2013. An updated version of this assessment (a revised Section 6 of the original application) was included in the January 30, 2013 submittal. In that version of this assessment, ENVIRON used a series of volume sources to represent the support vessels and crew boats emissions as they arrived at and departed from the drilling vessels, in a run designed to assess short-term Class II SILs. Subsequently, EPA’s Mr. Stan Krivo requested a more conservative modeling approach for these support vessels and crew boats. This version of the air quality impact assessment includes a revised treatment of the support vessels and crew boats for the short-term modeling, using point sources. A copy of the updated CALPUFF modeling files for the Developer and Discoverer Americas will be sent on DVD under separate cover. On January 22, 2013, the PM 2.5 

### Significant Impact Levels (SILs) and significant Monitoring Concentration (SMC) were vacated by the United States Court of Appeals for the District of Columbia Circuit. EPA issued draft guidance for PM 2.5 

### air quality impact assessments 1 

### on March 4, 2013. This guidance indicates that PSD compliance can be demonstrated in this case (direct emissions of PM 2.5 

### do not trigger PSD review) via a screening-level analysis. In the companion document submitted with this assessment entitled “Background PM 2.5 

### Analysis for the Eastern Gulf of Mexico Outer Continental Shelf”, ENVIRON provides a screening-level assessment of secondary PM 2.5 

### impacts, and shows that sources such as Statoil’s are unlikely to adversely affect NAAQS compliance. Nonetheless, to provide an added level of conservatism, ENVIRON has retained the assessment of direct PM 2.5 

### impacts in the original version of this document, and updated that assessment to reflect the addition information supplied after the original PSD application was submitted. ENVIRON applied computer-based dispersion modeling techniques to simulate dispersion of emissions attributable to the proposed exploration activities. The results of the modeling are

1 Available at http://www.epa.gov/ttn/scram/guidance/guide/Draft_Guidance_for_PM25_Permit_Modeling.pdfOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-2



### used to assess compliance with the PSD increments, the National Ambient Air Quality Standards (NAAQS) and Significance Impact Levels (SIL) for Class I and Class II areas. ENVIRON also used dispersion modeling techniques to assess Class I area PSD increments and degradation of regional visibility and other Air Quality Related Values (AQRVs). The dispersion modeling techniques employed in the analysis follow a basic set of EPA regulatory guidelines (40 CFR Part 51, Appendix W, revised November 9, 2005; referred to as the Guidelines). The Guidelines include recommendations for model selection, data preparation, and model application, but allow flexibility on a case-by-case basis.


## 6.1 **Dispersion Model Selection** ENVIRON based its selection of the dispersion model on the characteristics of the proposed emission sources associated with the Maersk Developer and the Transocean Discoverer Americas drilling vessels and dispersion phenomena that might produce the maximum ground level concentrations. ENVIRON used the CALPUFF/CALMET modeling system to estimate impacts of air pollutants at discrete receptors placed 25 nautical miles from the States’ seaward boundary and at Class I areas, because of its design for long-range transport applications beyond 50 km. The modeling domain is shown in Figure 4 below as the blue box labeled “Statoil OCS CALPUFF Domain.” ENVIRON also used the VISCREEN model (Version 88341) to perform the visibility analysis for the Additional Impacts Analysis. VISCREEN calculates the potential impact of a plume of specified emissions for specific transport and dispersion conditions. A Good Engineering Practice (GEP) stack height analysis of the sources included in the modeling indicates building downwash would occur under some meteorological conditions. However, given that the nearest receptors are located about 100 km from the source, building downwash effects will not significantly affect the results and have been ignored. In general, at source-receptor distances this great, the details of the initial plume rise have an insignificant effect on the predicted concentrations. This is because the plume (puffs) have had time to disperse sufficiently to fill the planetary boundary layer (PBL, or mixing height). The details of stack exit velocity or temperature at various engine loads have an insignificant effect, and only the magnitude of emissions has a significant effect on predicted concentrations.


## 6.2 **Model Application** ENVIRON applied CALPUFF using CALPUFF input parameters approved by EPA and the FWS. Note that EPA’s Mr. Stan Krivo requested that the Class I and Class II concentration assessments use a collection of CALPUFF control parameters that conflicts with the recommendation given in Appendix B of the IWAQM Report. He requested the concentration CALPUFF runs use MREG = MCHEM = MDRY = MWET = 0 (i.e. no chemistry, no deposition). ENVIRON understands that EPA has never officially accepted CALPUFF’s chemistry and deposition algorithms, but disagrees with this change in guidance and precedent. Nonetheless, in effort to expedite this permit application, ENVIRON has used the requested CALPUFF control parameters for all CALPUFF-predicted concentrations. Separate CALPUFF runs were generated for the FLMs as part of the AQRVs analysis. The FLMs have requested that CALPUFF be run with both chemistry and deposition to evaluate visibility impacts and deposition in the Class I areas.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-3



### 6.2.1 Source Characterization The primary NO X 

### and PM 2.5 

### emission sources associated with the proposed exploration activities consist of diesel-fired engines on the drilling vessels. Additionally, the OCS air regulations define the OCS source to include direct emissions from vessels servicing the OCS sources while en route to or from the source when within 25 miles of the facility. These rules require Statoil to consider impacts from the associated fleet of vessels that support the drilling vessel. Developer emission sources include the following:

 

### Main Generator Engines (8)

 

### Emergency Generator Engine (1)

 

### Cementing Unit Engines (2)

 

### Life Boats (4)

 

### Rescue Boat (1)

 

### Fuel Storage Vessels

 

### Fugitives (diesel fuel system)

 

### Support Vessels (e.g. crew boats)

 

### Welding and Painting Activities

Discoverer Americas emission sources include the following:

 

### Main Generator Engines (6)

 

### Emergency Generator Engine (1)

 

### Life Boats (6)

 

### Rescue Boat (1)

 

### Emergency Air Compressor Engines (2)

 

### Forklift Engines (2)

 

### Fuel Storage Vessels

 

### Fugitives (diesel fuel system)

 

### Support Vessels (e.g. crew boats)

 

### Welding, Cement/Mud Mixing, and Painting Activities

None of the associated vessels will have flare booms installed or conduct any flaring during the duration of the exploratory drilling operations.

The basis for the maximum short-term and annual emission rates modeled for these sources are discussed in Section 6.2.4 below.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-4 

### Figure 4 CALPUFF modeling domain (blue box), with “25 mile” receptors (red), Class I receptors (purple) and radii (light blue)LCC Northing, kmOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-5



### 6.2.2 Modeling Scenario Statoil is permitting the flexibility to use either the Maersk Developer or the Transocean Discoverer Americas drilling units at any given time to conduct exploratory drilling in the OCS of the Eastern Gulf of Mexico. Each drilling vessel and associated support vessels can operate under varying operating scenarios. Statoil considered multiple operating scenarios for each drilling vessel, including operations under a range of emissions and release parameters (including partial loads) and varying locations of associated support vessels. Because of the distance between the closest receptors and the emissions sources, ENVIRON concluded that maximum impacts would result from the highest short-term and long-term emission rate scenarios. For the short-term scenarios, this corresponds to the drilling vessels operating at maximum proposed load conditions. Note that this is not 100% load for each engine. The drilling vessel operators do not consider it safe to operate a single engine at 100% load, for fear of engine failure. They prefer to distribute the load between multiple engines for the sake of redundancy. Although these sources could operate at less than the maximum proposed load conditions, any changes in stack parameters resulting from the lower loads would not result in higher impacts at the modeled receptors, because the plume (puffs) are well-mixed within the PBL by the time they arrive at the receptors. For each of the two main drilling vessel scenarios ( Maersk Developer or Transocean Discoverer Americas ), Statoil has two sets of emission rates: short-term and long-term. The short-term emission rates are used for the following assessments:

 Class II 1-hour NO 2 

### SIL (NAAQS)

 Class I & II 24-hour PM 2.5 

### “SIL” (NAAQS & PSD Increment)

 Class I visibility impairment The long-term emission rates are used for the remaining assessments:

 Class II annual NO 2 

### SIL (NAAQS & PSD Increment)

 Class I & II annual PM 2.5 

### “SIL” (NAAQS & PSD Increment)

 Class I annual NO 2 

### SIL

 Class I annual Nitrogen deposition rate The EPA has not identified a regulatory-default model for secondary PM 2.5 

### . Therefore, only concentrations resulting from primary PM 2.5 

### emissions will be compared to the (recently rescinded) PM 2.5 

### SILs. The Developer maximum short-term emissions modeling analysis is based on five Main Generator engines operating at 60% load, auxiliary equipment (i.e., emergency generator engine, life boats, fast rescue boat and cementing unit engines) operatingOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-6



### at 100% load and hourly emissions for support vessels (Crew Boats and Supply Boats) are derived from the maximum engine operation for the respective vessels. Annual emissions for the annual modeling analysis are based on three Main Generator engines operating at 60% load, all auxiliary equipment at 100% load, and support vessels based on maximum engine operation for the proposed annual run time.

The Discoverer Americas maximum short-term emissions are based on four Main Generator engines operating at 80% load. The emergency generator engine operates at 70% load for testing purposes. Auxiliary equipment (i.e., emergency air compressor engines, forklift engines, life boats and fast rescue boat) operate at 100% load. Short-term support vessels (Crew Boats and Supply Boats) emission rates are derived from the maximum engine operating rates for the respective vessels. Annual emissions are based on three Main Generator engines operating at 35% load and the emergency generator engine operating at 70% load. Annual emissions also include all other auxiliary equipment at 100% load, and support vessels based on maximum engine operation for the proposed annual run time.

PM 2.5 

### emissions from cement and mud mixing activities in support of Discoverer Americas operations were included in the modeling. NO 2 

### and PM 2.5 

### emissions from welding and painting activities on all vessels were determined to be insignificant 2 

### and were not included in the assessment. Statoil is requesting authorization to allow the Maersk or the Transocean drilling vessels and their associated fleet to operate in any of Statoil’s lease blocks located within the eastern Gulf of Mexico. As such, Statoil represented worst-case dispersion conditions as follows: Each lease block has dimensions of approximately five kilometers by five kilometers. The closest point to shore is the northwest corner of the Desoto Canyon 143 lease block, which lies at 28.851 o 

### N and 87.424 o 

### W. For purposes of this modeling analysis, Statoil modeled all scenarios from this northwest corner. This location has been selected to represent the lease blocks as a whole because it is the closest location to shore and the nearest Class I area (Breton Wilderness). Therefore, Statoil expects these to be the maximum model-predicted impacts. The locations of the associated support vessels (i.e, Crew Boats and Offshore Support Vessels [OSV]) also can affect the impacts at the receptors. In actual operations, support vessels are most likely either located adjacent to the drilling vessels with only minimal emissions associated with lower engine speeds, or arriving/departing from the drilling vessels with higher emissions associated with higher engine speeds. Statoil has therefore included one crew boat and one OSV in the modeling scenario, and modeled them as “under way” rather than at idle near the drilling vessel. The long-term emissions are based on the maximum hourly engine operation multiplied by the total number of hours of each vessel class. The short-term emissions are based on the vessels operating simultaneously at maximum load. For the annual averaging period and Class I visibility modeling, Statoil modeled the support vessels as a series of volume sources placed along a line originating at the drilling vessel and extending out 25 (nautical) miles in the direction of the vessel’s home port (Port Fourchon,

2 

### Regulated air pollutants are less than 2 tpy and therefore insignificant per 40 CFR 71.5(c)(11)(ii).Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-7



### Louisiana). Modeling both support vessels’ emissions as a series of volume sources is conservative and appropriate for the maximum annual impacts. 3


### The line source algorithm in CALPUFF is essentially the same as the Buoyant Line Plume (BLP) model, which was developed to handle the unique situation of aluminum reduction plants. It is not appropriate for modeling the emissions of vessels underway. Instead, the emissions were distributed evenly among a series of ten (10) volume sources placed evenly along the line. Because the CALMET grid spacing is 4km, using a finer spacing would have little effect, as all the puffs originating within a grid box would “see” the same meteorology and be treated identically. For the short-term averaging period modeling, Statoil conservatively modeled the support vessels as stationary point sources. Both ships were assumed to be located at the same point, at the end of the 25-mile line closest to shore. Downwash was not included, because of the large distance to the nearest receptors which allows the puffs to expand to span the boundary layer – the details of the emissions points are not as important as the amount of emissions. All four of the Crew Boat’s main engines were assumed to be operating at 100% load, as were both of its generators. However, the Crew Boat bow thrusters were assumed to be not operating during transit. When the bow thruster engines are used the main engines are running at much lower loads, such that the total emissions for maneuvering are much smaller than during transit. Statoil also assumed the OSV emergency generator would not be operating during transit. Emissions attributable to cement handling and forklift operation were modeled as a volume source, centered on the main deck of the Discoverer Americas

. A summary of the two sets of emission rates used in the modeling analyses by operating scenario is presented below. It should be noted that the maximum short-term emission rates are used to model 1-hour NO 2 

### and 24-hour PM 2.5 

### concentrations at the 25-mile and Class I receptors, and to assess changes in visibility at Class I area receptors. The maximum annual emission rates are used to assess annual-average NO 2 

### and PM 2.5 

### concentrations at the 25-mile and Class I receptors, and deposition rates at Class I area receptors. Developer

 Maximum short-term (1-hour and 24-hour) emission rates: Five Main Generator engines at 60% load Auxiliary drilling vessel equipment (i.e., emergency generator, life boats, fast rescue boat and cementing unit engines) at 100% load OSV main engines at 100% load Crew boat main engines and generator engines at 100% load  Maximum annual emission rates:

3 

### Approach discussed and approved via the Protocol process.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-8 

### Three Main Generator engines at 60% load Auxiliary drilling vessel equipment (i.e., emergency generator, life boats, fast rescue boat and cementing unit engines) at 100% load OSV and Crew vessels present, based on maximum annual operation

Discoverer Americas

 Maximum short-term (1-hour & 24-hour) emission rates: Four Main Generator engines at 80% load Emergency Generator engine at 70% load (testing scenario) Auxiliary drilling vessel equipment (i.e., life boats, fast rescue boat, cement handling, forklift engines, and emergency air compressors) at 100% load OSV main engines at 100% load Crew boat main engines and generator engines at 100% load  Maximum annual emission rates: Three Main Generator engines at 35% load Emergency Generator engine at 70% load (testing scenario) Auxiliary drilling vessel equipment (i.e., life boats, fast rescue boat, cement handling, forklift engines, and emergency air compressors) at 100% load OSV and Crew vessels present, based on maximum annual operation

**6.2.3 Stack Parameters and Emission Rates** In addition to emission rates, the modeling analysis requires information regarding stack heights, building dimensions, and other exit parameters that characterize exhaust flow from emission points. These release characteristics have an important influence on the results of the analysis. Ultimately, Statoil used emission rates corresponding to the selected worst-case impact operating scenarios discussed in Section 6.2.2. Statoil used the stack parameters such as stack heights and other exit parameters that characterize exhaust flow from emission points in the dispersion modeling simulations. For stacks with a vertical or ≥ 45° upward angled discharge, Statoil used available stack parameter data (i.e., stack diameter, stack exit velocity, and stack exit temperature). For stacks with horizontal discharges, Statoil adjusted the stack parameters to remove the plume rise due to momentum yet maintain thermal plume rise, by using a stack exit velocity of 0.001 meters per second (m/s). Stack heights are relative to the surface of the water. Exhaust stack parameters for the Developer and Discoverer Americas drilling vessels are listed in Tables 6.2.3-1 and Table 6.2.3-2, respectively. Support vessel exhaust stack parameters are listed in Table 6.2.3-3. Stack parameters for emission sources modeled as volume sources for long-term and short-term scenarios are listed in Table 6.2.3-4 and Table 6.2.3-5, respectively.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-9 

### Table 6.2.3-1 **Developer Point Source Stack Parameters**  **Used in CALPUFF Modeling Analysis**

**Stack Modeling**  **ID X-Coord**  **Y-Coord Height**  **Elev. Dia.**  **Exit Vel.**  **Exit Temp.**  **Orientation (LCC)**  **(LCC) (m)**  **(m) (m)**  **(m/s) (K)**  Gen. Engine 1 GEN1 941.93 -1186.23 28.93 0 0.8 0.001 623.15 Horizontal Gen. Engine 2 GEN2 941.93 -1186.23 28.93 0 0.8 0.001 623.15 Horizontal Gen. Engine 3 GEN3 941.93 -1186.23 26.82 0 0.8 0.001 623.15 Horizontal Gen. Engine 4 GEN4 941.93 -1186.23 26.82 0 0.8 0.001 623.15 Horizontal Gen. Engine 5 GEN5 941.93 -1186.3 28.93 0 0.8 0.001 623.15 Horizontal Gen. Engine 6 GEN6 941.93 -1186.3 28.93 0 0.8 0.001 623.15 Horizontal Gen. Engine 7 GEN7 941.93 -1186.3 26.82 0 0.8 0.001 623.15 Horizontal Gen. Engine 8 GEN8 941.93 -1186.3 26.82 0 0.8 0.001 623.15 Horizontal

E. Gen Engine EGEN1 942.01 -1186.23 9.45 0 0.4 0.001 888.15 Downward with 45 degree angle to horizon Lifeboat 1 LB1 942.02 -1186.26 19.7 0 0.9 0.001 830.15 Horizontal Lifeboat 2 LB2 942.02 -1186.27 19.7 0 0.9 0.001 830.15 Horizontal Lifeboat 3 LB3 941.94 -1186.26 19.7 0 0.9 0.001 830.15 Horizontal Lifeboat 4 LB4 941.94 -1186.27 19.7 0 0.9 0.001 830.15 Horizontal MOB Engine 1 MOB1 941.93 -1186.26 19.7 0 1.9 0.001 773.15 Horizontal

Cement Unit Engine 1 CMU1 941.98 -1186.3 9.45 0 0.2 0.001 794.15 Downward with 45 degree angle to horizon

Cement Unit Engine 1 CMU2 941.98 -1186.3 9.45 0 0.2 0.001 794.15 Downward with 45 degree angle to horizonOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-10 

### Table 6.2.3-2 **Discoverer Americas Point Stack Parameters**  **Used in CALPUFF Modeling Analysis**

**Stack Modeling**  **ID X-Coord**  **Y-Coord Height**  **Elev. Dia.**  **Exit Vel.**  **Exit Temp.**  **Orientation (LCC)**  **(LCC) (m)**  **(m) (m)**  **(m/s) (K)**  Gen. Engine 1 GEN1 941.853 -1186.259 21.33 0 1 0.001 640 Horizontal Gen. Engine 2 GEN2 941.852 -1186.261 21.33 0 1 0.001 640 Horizontal Gen. Engine 3 GEN3 941.853 -1186.262 21.33 0 1 0.001 640 Horizontal Gen. Engine 4 GEN4 941.853 -1186.268 21.33 0 1 0.001 640 Horizontal Gen. Engine 5 GEN5 941.852 -1186.269 21.33 0 1 0.001 640 Horizontal Gen. Engine 6 GEN6 941.853 -1186.271 21.33 0 1 0.001 640 Horizontal E-Gen. Engine EGEN 942.063 -1186.25 21.33 0 0.6 0.001 640 Horizontal

Lifeboat 1 LB1 942.072 -1186.283 12.74 0 0.1 0.001 830.15 Horizontal Lifeboat 2 LB2 942.072 -1186.247 12.74 0 0.1 0.001 830.15 Horizontal Lifeboat 3 LB3 942.061 -1186.283 12.74 0 0.1 0.001 830.15 Horizontal Lifeboat 4 LB4 942.061 -1186.247 12.74 0 0.1 0.001 830.15 Horizontal Lifeboat 5 LB5 941.843 -1186.282 12.74 0 0.1 0.001 830.15 Horizontal Lifeboat 6 LB6 941.843 -1186.248 12.74 0 0.1 0.001 830.15 Horizontal MOB Engine 1 MOB 942.05 -1186.285 12.74 0 0.1 0.001 830.15 Horizontal Air Compressor 1 ACOMP1 941.843 -1186.282 15.85 0 0 0.001 773 Horizontal Air Compressor 2 ACOMP2 941.843 -1186.282 1.83 0 0 0.001 773 Horizontal



### Table 6.2.3
**- 3**  **Support Vessel Point Source Stack Parameters**  **Used in CALPUFF Modeling Analysis**

**Stack Modeling**  **ID X-Coord**  **(LCC) Y-Coord**  **(LCC) Height**  **(ft) Elev.**  **(ft) Diameter**  **(ft) Exit**  **Velocity**

**(ft/s) Exit**  **Temp**

**(K) Orientation** 

OSV (Main #1) OSV1 895.858 -1186.624 57.04 0 1.33 157.32 718 Vertical OSV (Main #2) OSV2 895.858 -1186.624 57.04 0 1.33 157.32 718 Vertical OSV (Main #3) OSV3 895.858 -1186.624 57.04 0 1.33 157.32 718 Vertical OSV (Main #4) OSV4 895.858 -1186.624 57.04 0 1.33 157.32 718 Vertical Crewboats (Main #1) C1 895.858 -1186.624 3.28 0 1.00 188.32 718 Horizontal Crewboats (Main #2) C2 895.858 -1186.624 3.28 0 1.00 188.32 607 Horizontal Crewboats (Main #3) C3 895.858 -1186.624 3.28 0 1.00 188.32 607 Horizontal Crewboats (Main #4) C4 895.858 -1186.624 3.28 0 1.00 188.32 607 Horizontal Crewboats (Generator #1) CG1 895.858 -1186.624 3.28 0 0.33 152.25 610 Horizontal Crewboats (Generator #2) CG2 895.858 -1186.624 3.28 0 0.33 152.25 610 HorizontalOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-11



### The volume sources used in the annual simulations to simulate the crew boat and offshore support vessels within 25 miles of the drilling vessels require a height, elevation, and initial lateral (σ y 

### ) and vertical (σ z 

### ) dispersion parameters. The elevation was taken to be zero (mean sea level) and the volume height was set to the average of the Crew Boat and OSV heights: 5.39 m and 33.42 m, respectively. The initial vertical dispersion Sigma-Z was taken as the average boat height divided by 2.15, and the initial horizontal dispersion Sigma-Y was calculated using the center-to-center distance between adjacent volume sources divided by 2.15, following the guidance provided in EPA (1995) 4



### . The volume source used to represent the miscellaneous sources (cement handling and forklift usage aboard the Discoverer Americas ) was assumed to be located on the drilling vessel’s main deck, 2.47 meters above water level. The initial plume height and Sigma-Z were based on an assumed height of 3m, and the initial Sigma-Y was assumed to be 10m. Maximum short-term (1-hour and 24-hour) and annual emission rates for these sources are summarized in Tables 6.2.3-6 through 6.2.3-19.

4 

### ISCST3 Users Guide (EPA, 1995): Line source representation by adjacent volume sources. 

### Table 6.2.3- **4** 

### Volume Source Stack Parameters for Support Vessels and Miscellaneous Sources **Used in Visibility and Long-Term CALPUFF Modeling Analysis**
**ID X-UTM**  **Y- UTM Height (m)**  **Elev (m) Sigma Y (m)**  **Sigma Z (m)** VOL01 

### 895.858 -1186.62 19.41 0 

### 2382 18.1 VOL02 

### 900.98

- 1186.58 19.41 0 

### 2382 18.1 VOL03 

### 906.101

- 1186.55 19.41 0 

### 2382 18.1 VOL04 

### 911.223

- 1186.51 19.41 0 

### 2382 18.1 VOL05 

### 916.345

- 1186.47 19.41 0 

### 2382 18.1 VOL06 

### 921.467 -1186.43 19.41 0 

### 2382 18.1 VOL07 

### 926.589

- 1186.39 19.41 0 

### 2382 18.1 VOL08 

### 931.71 -1186.35 19.41 0 

### 2382 18.1 VOL09 

### 936.832

- 1186.31 19.41 0 

### 2382 18.1 VOL10 941.954 -1186.267 19.41 0 

### 2382 18.1 MISC (a) 941.964 -1186.269 1.5 2.74 10 1.4 (a) MISC used to represent cement handling and the forklift, applicable only to the Discoverer Americas



### Table 6.2.3-5 **Volume Source Stack Parameters for Miscellaneous Sources Used in Short-Term CALPUFF Modeling Analysis** 
**ID X-UTM**  **Y- UTM Height (m)**  **Elev (m) Sigma Y (m)**  **Sigma Z (m)** MISC (a) 941.964 -1186.269 1.5 2.74 10 1.4 (a) MISC used to represent cement handling and the forklift, applicable only to the Discoverer AmericasOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-12 

### Table 6.2. **3**
**- 6**  **Short-Term Emission Rates from Stacks**

**Used in Developer**  **CALPUFF Modeling Analysis** 
**Source ID NO**  **X (lb/hr)**  **SO 2**  **(lb/hr) PM**  **2.5 (lb/hr)**  GEN1 53.53 0.04 0.98 GEN2 53.53 0.04 0.98 GEN3 53.53 0.04 0.98 GEN4 53.53 0.04 0.98 GEN5 53.53 0.04 0.98 GEN6 0.00 0.00 0.00 GEN7 0.00 0.00 0.00 GEN8 0.00 0.00 0.00 EGEN1 38.58 0.03 0.99 LB1 0.36 0.0003 0.02 LB2 0.36 0.0003 0.02 LB3 0.36 0.0003 0.02 LB4 0.36 0.0003 0.02 MOB1 2.01 0.002 0.09 CMU1 5.92 0.005 0.13 CMU2 5.92 0.005 0.13



### Table 6. **2. 3** 
**- 7**  **Short-term Speciated Emission Rates from Stacks**

**Used in Developer**  **CALPUFF Modeling Analysis**
**Source ID**  **SO 2**  **(g/s) SO**  **4 (g/s)**  **NO x**  **(g/s) HNO**  **3 (g/s)**  **NO 3**  **(g/s) EC (g/s)**  **SOA (g/s) PMC**  **(g/s) PMF**  **(a) (g/s)**  GEN1 5.47E-03 2.97E-03 6.75E+00 0 1.54E-04 9.19E-02 2.78E-02 0 0 GEN2 5.47E-03 2.97E-03 6.75E+00 0 1.54E-04 9.19E-02 2.78E-02 0 0 GEN3 5.47E-03 2.97E-03 6.75E+00 0 1.54E-04 9.19E-02 2.78E-02 0 0 GEN4 5.47E-03 2.97E-03 6.75E+00 0 1.54E-04 9.19E-02 2.78E-02 0 0 GEN5 5.47E-03 2.97E-03 6.75E+00 0 1.54E-04 9.19E-02 2.78E-02 0 0 GEN6 0 0 0 0 0 0 0 0 0 GEN7 0 0 0 0 0 0 0 0 0 GEN8 0 0 0 0 0 0 0 0 0 EGEN1 3.49E-03 2.99E-03 4.86E+00 0 1.55E-04 9.27E-02 2.81E-02 0 0

LB1 3.97E-05 6.88E-05 4.51E-02 0 3.57E-06 2.13E-03 6.45E-04 0 0 LB2 3.97E-05 6.88E-05 4.51E-02 0 3.57E-06 2.13E-03 6.45E-04 0 0 LB3 3.97E-05 6.88E-05 4.51E-02 0 3.57E-06 2.13E-03 6.45E-04 0 0 LB4 3.97E-05 6.88E-05 4.51E-02 0 3.57E-06 2.13E-03 6.45E-04 0 0 MOB1 2.23E-04 2.58E-04 2.53E-01 0 1.34E-05 7.98E-03 2.42E-03 0 0 CMU1 6.85E-04 3.95E-04 7.46E-01 0 2.05E-05 1.22E-02 3.71E-03 0 0 CMU2 6.85E-04 3.95E-04 7.46E-01 0 2.05E-05 1.22E-02 3.71E-03 0 0 

### ( a) Speciation above provided for CALPUFF visibility runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-13 

### Table 6.2. **3**
**- 8**  **Long-Term Emission Rates From Stacks**

**Used In Developer**  **CALPUFF Modeling Analysis** 
**Source ID NO**  **X (tpy)**  **SO 2**  **(tpy) PM**  **2.5 (tpy)**  GEN1 115.63 0.09 2.13 GEN2 115.63 0.09 2.13 GEN3 115.63 0.09 2.13 GEN4 0 0 0 GEN5 0 0 0 GEN6 0 0 0 GEN7 0 0 0 GEN8 0 0 0 EGEN1 0.76 0.007 0.02 LB1 0.002 0.000002 0.0001 LB2 0.002 0.000002 0.0001 LB3 0.002 0.000002 0.0001 LB4 0.002 0.000002 0.0001 MOB1 0.01 0.00001 0.0005 CMU1 0.18 0.0002 0.004 CMU2 0.18 0.0002 0.004



### Table 6.2. **3**
**- 9**  **Long-Term Speciated Emission Rates from Stacks**

**Used in Developer**  **CALPUFF Modeling Analysis Source**  **ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s) SOA (g/s)**  **PMC (g/s)**  **PMF (**  **a )**  **(g/s)** GEN1 2.70E-03 1.46E-03 3.33E+00 0 7.58E-05 4.53E-02 1.37E-02 0 0 GEN2 2.70E-03 1.46E-03 3.33E+00 0 7.58E-05 4.53E-02 1.37E-02 0 0 GEN3 2.70E-03 1.46E-03 3.33E+00 0 7.58E-05 4.53E-02 1.37E-02 0 0 GEN4 0 0 0 0 0 0 0 0 0 GEN5 0 0 0 0 0 0 0 0 0 GEN6 0 0 0 0 0 0 0 0 0 GEN7 0 0 0 0 0 0 0 0 0 GEN8 0 0 0 0 0 0 0 0 0 EGEN1 1.57E-05 1.35E-05 2.19E-02 0 6.99E-07 4.18E-04 1.26E-04 0 0 LB1 5.44E-08 9.42E-08 6.17E-05 0 4.88E-09 2.92E-06 8.84E-07 0 0 LB2 5.44E-08 9.42E-08 6.17E-05 0 4.88E-09 2.92E-06 8.84E-07 0 0 LB3 5.44E-08 9.42E-08 6.17E-05 0 4.88E-09 2.92E-06 8.84E-07 0 0 LB4 5.44E-08 9.42E-08 6.17E-05 0 4.88E-09 2.92E-06 8.84E-07 0 0 MOB1 3.06E-07 3.53E-07 3.47E-04 0 1.83E-08 1.09E-05 3.31E-06 0 0 CMU1 4.69E-06 2.71E-06 5.11E-03 0 1.40E-07 8.39E-05 2.54E-05 0 0 CMU2 4.69E-06 2.71E-06 5.11E-03 0 1.40E-07 8.39E-05 2.54E-05 0 0 (a) Speciation above provided for CALPUFF deposition runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-14 

### Table 6.2. **3**
**- 10**  **Short-Term Emission Rates From Stacks Used**

**In Discoverer Americas**  **CALPUFF Modeling Analysis**  **Source ID NO**  **X (lb/hr)**  **SO 2**  **(lb/hr) PM**  **2.5 (lb/hr)**  GEN1 127.04 0.08 1.85 GEN2 127.04 0.08 1.85 GEN3 127.04 0.08 1.85 GEN4 127.04 0.08 1.85 GEN5 0 0 0 GEN6 0 0 0 EGEN 42.31 0.02 0.84 LB1 0.44 0.0004 0.03 LB2 0.44 0.0004 0.03 LB3 0.44 0.0004 0.03 LB4 0.44 0.0004 0.03 LB5 0.44 0.0004 0.03 LB6 0.44 0.0004 0.03 MOB 2.61 0.002 0.11 ACOMP1 0.78 0.0003 0.05 ACOMP2 1.05 0.0004 0.07



### Table 6.2. **3**
**- 11**  **Short-Term Speciated Emission Rates From Stacks Used In**  **Discoverer Americas CALPUFF Modeling Analysis** 

**Source ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s) SOA (g/s)**  **PMC (g/s)**  **PMF (a)**  **(g/s)** GEN1 1.03E-02 5.58E-03 1.60E+01 0 2.89E-04 1.73E-01 5.24E-02 0 0 GEN2 1.03E-02 5.58E-03 1.60E+01 0 2.89E-04 1.73E-01 5.24E-02 0 0 GEN3 1.03E-02 5.58E-03 1.60E+01 0 2.89E-04 1.73E-01 5.24E-02 0 0 GEN4 1.03E-02 5.58E-03 1.60E+01 0 2.89E-04 1.73E-01 5.24E-02 0 0 GEN5 0 0 0 0 0 0 0 0 0 GEN6 0 0 0 0 0 0 0 0 0 EGEN 2.97E-03 2.54E-03 5.33E+00 0 1.32E-04 7.88E-02 2.39E-02 0 0 LB1 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 LB2 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 LB3 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 LB4 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 LB5 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 LB6 4.93E-05 8.54E-05 5.59E-02 0 4.43E-06 2.65E-03 8.01E-04 0 0 MOB 2.90E-04 3.35E-04 3.29E-01 0 1.74E-05 1.04E-02 3.14E-03 0 0 ACOMP1 3.42E-05 1.61E-04 9.76E-02 0 8.34E-06 4.98E-03 1.51E-03 0 0 ACOMP2 4.66E-05 2.19E-04 1.33E-01 0 1.13E-05 6.78E-03 2.05E-03 0 0 (a) Speciation above provided for CALPUFF visibility runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-15 

### Table 6.2. **3**
**- 1**  **2 Long-Term Emission Rates From Stacks Used In**  **Discoverer Americas CALPUFF Modeling Analysis** 

**Source ID NO**  **X (tpy)**  **SO 2**  **(tpy) PM**  **2.5 (tpy)**  GEN1 140.8 0.08 1.75 GEN2 140.8 0.08 1.75 GEN3 140.8 0.08 1.75 GEN4 0 0 0 GEN5 0 0 0 GEN6 0 0 0 EGEN 0.88 0.0005 0.02 LB1 0.003 0.000002 0.0002 LB2 0.003 0.000002 0.0002 LB3 0.003 0.000002 0.0002 LB4 0.003 0.000002 0.0002 LB5 0.003 0.000002 0.0002 LB6 0.003 0.000002 0.0002 MOB 0.02 0.00001 0.0007 ACOMP1 0.002 8.15E-7 0.00016 ACOMP2 0.003 1.11E-6 0.00022



### Table 6.2. **3**
**- 1**  **3 Long-Term Speciated Emission Rates From Stacks Used In**  **Discoverer Americas CALPUFF Modeling Analysis**  **Source ID**  **SO 2**  **(g/s) SO**  **4 (g/s)**  **NO x**  **(g/s) HNO**  **3 (g/s)**  **NO 3**  **(g/s) EC**  **(g/s) SOA**  **(g/s) PMC**  **(g/s) PMF**  **( a**  **) (g/s)**  GEN1 2.22E-03 1.20E-03 4.05E+00 0 6.24E-05 3.73E-02 1.13E-02 0 0 GEN2 2.22E-03 1.20E-03 4.05E+00 0 6.24E-05 3.73E-02 1.13E-02 0 0 GEN3 2.22E-03 1.20E-03 4.05E+00 0 6.24E-05 3.73E-02 1.13E-02 0 0 GEN4 0 0 0 0 0 0 0 0 0 GEN5 0 0 0 0 0 0 0 0 0 GEN6 0 0 0 0 0 0 0 0 0 EGEN 1.40E-05 1.20E-05 2.52E-02 0 6.23E-07 3.73E-04 1.13E-04 0 0 LB1 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 LB2 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 LB3 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 LB4 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 LB5 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 LB6 6.75E-08 1.17E-07 7.66E-05 0 6.06E-09 3.62E-06 1.10E-06 0 0 MOB 3.98E-07 4.59E-07 4.51E-04 0 2.38E-08 1.42E-05 4.31E-06 0 0 ACOMP1 2.35E-08 1.10E-07 6.69E-05 0 5.71E-09 3.41E-06 1.03E-06 0 0 ACOMP2 3.19E-08 1.50E-07 9.10E-05 0 7.77E-09 4.64E-06 1.41E-06 0 0 (a) Speciation above provided for CALPUFF deposition runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-16 

### Table 6.2.3
**- 14**  **Short-Term Emission Rates from Stacks Used in**

**Support Vessel CALPUFF Modeling Analysis** 
**Source ID NO**  **X (lb/hr)**  **SO 2**  **(lb/hr) PM**  **2.5 (lb/hr)**  OSV1 42.41 0.03 0.92 OSV2 42.41 0.03 0.92 OSV3 42.41 0.03 0.92 OSV4 42.41 0.03 0.92 C1 21.30 0.02 0.47 C2 21.30 0.02 0.47 C3 21.30 0.02 0.47 C4 21.30 0.02 0.47 CG1 1.48 0.00 0.05 CG2 1.48 0.00 0.05



### Table 6.2.3-15 **Short-term Speciated Emission Rates from Stacks Used in Support Vessel CALPUFF Modeling Analysis** 

**Source ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s) SOA (g/s)**  **PMC (g/s)**  **PMF (a)**  **(g/s)** OSV1 3.24E-03 2.78E-03 5.34E+00 0 1.44E-04 8.60E-02 2.60E-02 0 0 OSV2 3.24E-03 2.78E-03 5.34E+00 0 1.44E-04 8.60E-02 2.60E-02 0 0 OSV3 3.24E-03 2.78E-03 5.34E+00 0 1.44E-04 8.60E-02 2.60E-02 0 0 OSV4 3.24E-03 2.78E-03 5.34E+00 0 1.44E-04 8.60E-02 2.60E-02 0 0 C1 2.46E-03 1.42E-03 2.68E+00 0 7.37E-05 4.41E-02 1.33E-02 0 0 C2 2.46E-03 1.42E-03 2.68E+00 0 7.37E-05 4.41E-02 1.33E-02 0 0 C3 2.46E-03 1.42E-03 2.68E+00 0 7.37E-05 4.41E-02 1.33E-02 0 0 C4 2.46E-03 1.42E-03 2.68E+00 0 7.37E-05 4.41E-02 1.33E-02 0 0 CG1 1.71E-04 1.48E-04 1.86E-01 0 7.67E-06 4.58E-03 1.39E-03 0 0 CG2 1.71E-04 1.48E-04 1.86E-01 0 7.67E-06 4.58E-03 1.39E-03 0 0 (a) Speciation above provided for CALPUFF visibility runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-17 

### Table 6.2.3
**- 1**  **6 Long-Term Emission Rates From Stacks Used In** 

**Support Vessel CALPUFF Modeling Analysis** 
**Source ID NO**  **X (tpy)**  **SO 2**  **(tpy) PM**  **2.5 (tpy)**  OSV1 54.49 0.03 1.18 OSV2 54.49 0.03 1.18 OSV3 0.00 0.00 0.00 OSV4 0.00 0.00 0.00 C1 6.58 0.01 0.15 C2 6.58 0.01 0.15 C3 6.58 0.01 0.15 C4 6.58 0.01 0.15 CG1 0.46 0.00 0.02 CG2 0.46 0.00 0.02



### Table 6.2.3
**- 1**  **7 Long-Term Speciated Emission Rates from Stacks**  **Used in Support Vessel**  **CALPUFF Modeling Analysis Source**  **ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s) SOA (g/s)**  **PMC (g/s)**  **PMF (a)**  **(g/s)** OSV1 9.51E-04 8.15E-04 1.57E+00 0 4.22E-05 2.52E-02 7.64E-03 0 0 OSV2 9.51E-04 8.15E-04 1.57E+00 0 4.22E-05 2.52E-02 7.64E-03 0 0 OSV3 0 0 0 0 0 0 0 0 0 OSV4 0 0 0 0 0 0 0 0 0 C1 1.74E-04 1.00E-04 1.89E-01 0 5.20E-06 3.11E-03 9.42E-04 0 0 C2 1.74E-04 1.00E-04 1.89E-01 0 5.20E-06 3.11E-03 9.42E-04 0 0 C3 1.74E-04 1.00E-04 1.89E-01 0 5.20E-06 3.11E-03 9.42E-04 0 0 C4 1.74E-04 1.00E-04 1.89E-01 0 5.20E-06 3.11E-03 9.42E-04 0 0 CG1 1.21E-05 1.04E-05 1.31E-02 0 5.41E-07 3.23E-04 9.79E-05 0 0 CG2 1.21E-05 1.04E-05 1.31E-02 0 5.41E-07 3.23E-04 9.79E-05 0 0 (a) Speciation above provided for CALPUFF deposition runs, but EPA runs assumed all PM 2.5 emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-18 

### Table 6.2. **3**
**- 1**  **8 Short-Term Emission Rates From Volume Sources Used In**  **Discoverer Americas CALPUFF Modeling Analysis** 

**Source ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s)**  **SOA (g/s)**  **PMC (g/s)**  **PMF (a)**  **(g/s)** Forklift 1.37E-04 0 9.74E-02 0 0 0 0 0 2.48E-03 Cement 0 0 0 0 0 0 0 0 4.77E-02 MISC (sum) 5.26E-02 (a) All PM 2.5 assumed emitted as PMF.



### Table 6.2. **3**
**- 1**  **9 Long-Term Emission Rates From Volume Sources Used In**  **Discoverer Americas CALPUFF Modeling Analysis** 

**Source ID SO**  **2 (g/s)**  **SO 4**  **(g/s) NO**  **x (g/s)**  **HNO 3**  **(g/s) NO**  **3 (g/s)**  **EC (g/s)**  **SOA (g/s)**  **PMC (g/s)**  **PMF (a)**  **(g/s)** Forklift 1.86E-06 0 1.31E-02 0 0 0 0 0 6.69E-05 Cement 0 0 0 0 0 0 0 0 2.35E-05 MISC (sum) 2.36E-02 (a) All PM 2.5 assumed emitted as PMF.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-19



### 6.2.4 Building Downwash (Prime Algorithm) Building downwash is the effect of nearby structures on the flow of emissions from their respective sources. However, as discussed in Section 6.1, ENVIRON did not account for building downwash effects as part of the 25-mile receptor modeling approach. Given that the nearest receptors are located about 100 km from the source, building downwash effects will not significantly affect the modeled results. The FLMs typically do not request downwash be included, and neither “downwash” nor “BPIP” are mentioned in either FLAG (2000) or FLAG (2010). **6.2.5 Receptor Locations** EPA has established a policy for EGOM of using receptors placed 25 nautical miles from the nearby States’ seaward boundaries. These discrete 25-mile receptors were generated using the State seaward boundaries for Louisiana, Mississippi, Alabama, and Florida. The boundaries extend for up to the three nautical miles for Louisiana, Mississippi and Alabama and up to nine nautical miles for Florida 5 

### . ENVIRON placed discrete receptors approximately 1 km apart. The location of these receptors is shown in Figure 4 above as red dots (Note: receptors may appear as a solid red line in Figure 4 due to low resolution). All these receptors are over water. Therefore, terrain elevations were not used for the Class II analysis: all receptors were assigned an elevation of 0 m (i.e., sea level). **6.2.6 Meteorological Data** Statoil used a three-year meteorological CALMET dataset (2001 – 2003) which was prepared for the Visibility Improvement State and Tribal Association of the Southeast (VISTAS) – Best Available Retrofit Technology (BART) modeling. Specifically, the 4-km VISTAS Domain 2 dataset was used for the modeling analysis, for both the Class I and Class II assessments. The three year CALPUFF-ready meteorological dataset was provided by the North Carolina Department of Environment and Natural Resources (NC DENR). This is the most recent version developed by the FLMs, using the currently approved regulatory version of CALMET (Version 5.8, level 070623). The CALPUFF computational grid was taken to be a subset of the full VISTAS grid, using points 1 to 186 in the X direction (East) and points 56 to 163 in the Y direction (North). This sub-domain, along with the full VISTAS domain, is shown in Figure 4, and includes a 50 km buffer past the Class I area. The domain was extended far enough to the East to include the 25-mile receptors along Western Florida, and far enough South to include a 100 km buffer around the drill rig location to allow for re-circulation of puffs.


## 6.3 **Project Impact Assessment** This section assesses the magnitude of concentration impacts resulting from emissions from the proposed Statoil exploration activities at the discrete 25-mile receptors. If a pollutant’s calculated concentration exceeds the EPA SIL for that pollutant, the impacts of the facility must be assessed in the context of other increment-consuming sources to evaluate total increment consumption. Exceeding a SIL also requires that the facility’s compliance with the applicable NAAQS be evaluated, taking into account background concentrations and the contributions of significant regional sources.

5 U. S. Commission on Ocean Policy. Primer on Ocean Jurisdictions: Drawing Lines in the Water. Final Report.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-20



### The attached report summarizes PM 2.5 

### in the EGOM region. It provides support for the use of the PM 2.5 

### SILs (for sources that exceed the PSD Significant Emission Rate for PM 2.5 

### , which isnot the case in this application) and provides a summary of data to be used in lieu of preconstruction monitoring data. It also contains a qualitative discussion of secondary PM 2.5 

### that may arise from NO X 

### /SO 2 

### emissions originating in the EGOM. Although the attached report is not specific to Statoil’s proposed emissions, it shows that emissions in the range of those covered by this PSD permit application are not likely to cause or contribute to an exceedance of the PM 2.5 

### NAAQS on shore. As discussed previously, ENVIRON applied the CALPUFF/CALMET modeling system to simulate pollutant dispersion for three years of hourly meteorological data. ENVIRON determined the highest concentrations for each discrete receptor. This section discusses the results of the modeling assessment.

**6.3.1 Class II Criteria Pollutant Concentrations** ENVIRON modeled the criteria pollutant concentrations using the emission rates presented above in Tables 6.2.3-6 through 6.2.3-8 and Tables 6.2.3-9 through 6.2.3-12 for Developer and Discoverer Americas drilling vessels, respectively, for comparison to the SIL and SMC for NO 2 6



### . Although the SILs and SMC for PM 2.5 

### have been vacated, we present the PM 2.5 

### results and compare them to the (former) SILs as an added level of conservatism. In order to assess the significance of the predictions, ENVIRON compared the 3-year average maximum NO 2 

### concentrations at the discrete 25-mile receptors predicted by CALPUFF with the Class II PSD SIL for NO 2 

### . NOx was assumed to be 80% converted to NO 2 

### , consistent with a “Tier 2” approach. ENVIRON also compared the maximum PM 2.5 

### concentrations to the Class II PSD SIL for PM 2.5 

### . Although the PSD SIL and SMC for PM 2.5 

### were recently rescinded, they are deemed appropriate as measures of significance in this case. Justification for this decision is found in the attached report, “Background PM 2.5 

### Analysis for the Eastern Gulf of Mexico Outer Continental Shelf”. These Class II receptors with concentrations below the SILs are considered to be “insignificantly affected” and these pollutants do not require assessments of the Class II increments or NAAQS. ENVIRON compared the maximum criteria pollutant concentrations at the discrete 25-mile receptors predicted by CALPUFF with the applicable SMC for NO 2 

### and PM 2.5 

### . If the highest modeled concentration caused by the proposed significant emissions increase is above the SMC, then a demonstration of pre-construction ambient NO 2 

### or PM 2.5 

### levels would be required. However, no monitoring is required if modeling results of the significance analysis are below the defined SMC for NO 2 

### and PM 2.5 

### .

6 It has been EPA's longstanding policy under the New Source Review and PSD programs to allow the use of

Significant Impact Levels (SILs) to assess whether a proposed new or modified stationary source causes or contributes to a violation of the NAAQS or PSD Class II increments (40 CFR 51.165 (b)(2)). Sources with pollutant concentrations under the SILs are considered insignificant, whether or not background or other increment consuming sources affect the applicable pollutant concentration and averaging period of concern. The SIL criteria are only intended to apply to the ambient standards and Class II increments, not the Class I increments or the need to conduct an AQRV analysis (see, for example, Calcagni, 1991). Note that the use of the term "significant" impact level in the PSD program does not imply a “significant adverse impact” in a NEPA sense, nor does it imply exceedances of ambient standards established to protect health and welfare.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-21



### The results of the CALPUFF modeling analysis are compared to the applicable SILs and SMCs in Table 6.3.1-1. Because the maximum predicted concentrations on 1-hour, 24-hour, and annual average are less than the applicable SILs, the project is deemed to not cause or contribute to a violation of the NAAQS or PSD increments for these pollutants. Furthermore, the maximum predicted NO 2 

### concentrations are less than the applicable SMC; therefore, no monitoring is required.

**Table 6.3.1-1 Maximum CALPUFF-Predicted Class II Concentrations** 

**Criteria Pollutant**  **Averaging Period**  **Developer Max.**  **Concentration (μg/m**  **3 )**  **Discoverer Americas**  **Max. Concentration**  **(μg/m 3**  **) Modeling**  **Significance Level**  **(μg/m 3**  **) Monitoring**  **DeMinimus Concentration**  **(μg/m 3**  **)**

NO 2 a 1-hr 5.7 7.3 7.5 c None c Annual 0.03 0.04 1.0 14

PM 2.5 24-hr b 0.08 0.10 1.2 d 4 d
Annual 0.0009 0.0008 0.3 d None

Notes:

a Annual NO X was assumed to be 75 percent converted to NO 2 . One-hour NO 2 model prediction based on the three year average of the maximum daily model-predicted 1-hour NO X concentration at each receptor location and 80 percent conversion to NO 2 (Tier II of EPA’s June 28, 2010 memo “Guidance Concerning the Implementation of the 1-hour NO 2 NAAQS for the Prevention of Significant Deterioration Program.”
b 100 th percentile (maximum) values are presented (not 98 th percentile) using direct PM 2.5 emissions only.

c Interim SIL, established June 28, 2010 in the memo “Guidance Concerning the Implementation of the 1-hour NO 2 NAAQS for the Prevention of Significant Deterioration Program”. The 1-hour NO 2 Monitoring DeMinimus level has not yet been proposed.
d The PM 2.5 SILs and SMC were vacated on January 22, 2013,but presented here for comparison.



## 6.4 **Class I Air Quality Related Values Analysis** PSD guidance requires an analysis of potential impacts to AQRVs in Federal Class I areas within 100 km (62.1 miles) of the facility from pollutants emitted by the project subject to PSD review. However, Federal Land Managers (FLMs) typically request analyses of AQRV impacts for Class I areas within 200 km (124 miles) of the site. Best Available Retrofit Technology (BART) exemption and determination modeling under EPA’s Regional Haze Regulations require that Class I areas within 300 km (186 miles) be included. A larger domain similar to that developed for BART modeling was used for this analysis, resulting in the inclusion of Class I areas beyond those usually required for a PSD analysis. Figure 4 presented above documents the CALPUFF modeling domain with the selected Class I area. As shown previously in Figure 4, there is one Class I area within 300 km of the facility. The nearest Class I area, the Breton Wilderness Area, is located at a distance of 175 km (109 miles) from the nearest proposed OCS Project lease block area. Statoil contacted the FWS to discuss the proposed OCS Project and AQRV analysis. Statoil also submitted the modeling protocol toOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-22



### the FWS on July 23, 2012, which was subsequently approved on July 30, 2012. 7 

### The distances from the proposed Statoil exploration activities to the four closest Class I areas considered in this analysis are listed in Table 6.4-1.

**Table 6.4-1 Nearest Distance to Class I Area from Proposed Project**  **ID Class I Area**  **Distance 1**  

### (Km) BRET Breton Wilderness Area 175 BRBA Bradwell Bay Wilderness Area 307 STMA Saint Marks Wilderness Area 313 CHAS Chassahowitzka Wilderness Area 641 Notes:

a Distance to the northwest corner of Desoto Canyon 143 lease block (28.85064 o N and 87.42378 o W)



### The Breton, Chassahowitzka, and Saint Marks Wilderness Areas are managed by the FWS. The Bradwell Bay Wilderness Area is managed by the FS. The AQRVs of concern include visibility, soil, flora, fauna, and aquatic resources. The CALPUFF modeling system is currently recommended for evaluating impacts to AQRVs in Class I areas affected by long-range transport. Potential impacts are characterized based on predictions of total nitrogen and/or sulfur deposition flux, change in light extinction, and pollutant concentrations. Pollutant concentration predictions were also used to assess Class I area increment consumption for pollutants subject to PSD review.

**6.4.1 Model Selection** On April 15, 2003, EPA adopted the CALPUFF modeling system as the EPA’s preferred model for long-range transport assessments and for evaluating potential impacts to Class I areas by including CALPUFF in Appendix A of the Guidelines. Features of the CALPUFF modeling system include the ability to consider: secondary aerosol formation; gaseous and particle deposition; wet and dry deposition processes; complex three-dimensional wind regimes; and the effects of humidity on regional visibility. As is currently required, CALPUFF Version 5.8 (release date June 23, 2007) was used; except for CALPOST, for which version 6.221 (release date July 24, 2008) was used 8



### . **6.4.2 Modeling Procedures** The modeling procedures used for the Class I area analyses followed the recommendations of the Interagency Agency Workgroup on Air Quality Modeling (IWAQM) and the FLM Air Quality Related Values Workgroup (FLAG), outlined in the FLAG Phase I Report - Revised (November 10, 2010). EPA endorsed these procedures in advance of the IWAQM Phase II report (December 1998), and reiterated this endorsement in the April 15, 2003 Federal Register notice (Volume 68, Number 72) that adopted CALPUFF as a Guideline model. EPA further clarified

7 Email correspondence from Jill Webster, dated July 30, 2012. 8 

### See http://www.epa.gov/ttn/scram/dispersion_prefrec.htm#calpuffOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-23



### their required CALMET setting in a memo issued on August 31, 2009 (Fox 2009). 9 

### However, EPA’s Mr. Stan Krivo requested that the CALPUFF runs used to assess Increment (SILs) use no chemical transformation or deposition. Statoil therefore performed two sets of CALPUFF runs, one following the IWAQM Phase II report (MCHEM = MDRY = MWET = 1) for the FLMs, to assess visibility degradation and S/N deposition; and one contradicting IWAQM (MCHEM = MDRY = MWET = 0) for the EPA to assess Class I SILs for Increment. **6.4.3 Model Setup and Application** The CALPUFF modeling system is equipped with a host of modeling options, but, as stated in the previous section, ENVIRON used the procedures and defaults recommended by the FLAG Phase I Report. Any deviations from the defaults were approved by the FLM. CALPUFF control parameters are listed in Appendix A of the Modeling Protocol. For the regional haze assessment using the CALPUFF modeling system, particulate matter emission rates must be speciated into six fractions: soot or elemental carbon (EC), PM fine (PMF), PM coarse (PMC), organic carbon (OC), sulfate (SO 4 

### ), and nitrate (NO 3 

### ). Tables provided in Section 6.2.3 presented the speciated particulate matter emission rates used in the analysis. The speciation was based on speciation profiles recommended for aerosol modeling by the EPA. 10 

### Sources in the database are referenced by Source Classification Code (SCC), and the database provided information for speciating the fine fraction into the other components required by CALPUFF. All the emission units are diesel-fired and appropriate SCC codes were chosen. The CALPUFF modeling conservatively used the maximum short-term emission rate (1-hour) for the short-term assessment assessments. As previously discussed, the maximum short-term emission rates for support vessels are based on maximum engine operation for the entire 24- hour period. Maximum short-term emission rates for main engines on the drill rigs are based on maximum expected hourly operating loads, as discussed in Section 6.2.3. **6.4.4 Averaging Periods** CALPUFF-predicted hourly pollutant concentrations were averaged for comparison with applicable 1-hour and annual NO 2 

### and 24-hour and annual PM 2.5 

### Class I SILs and PSD increments. Predicted extinction coefficients and total deposition fluxes were calculated as 24- hour and annual averages, respectively. In all instances, comparisons with regulatory criteria were based on the highest model-prediction of the three-year simulation for the averaging period.

**6.4.5 Chemical Transformations** The NO X 

### chemistry in CALPUFF depends on the ambient ammonia concentration to establish the equilibrium between gaseous nitric acid and ammonium nitrate. However, ambient ammonia concentrations are not explicitly simulated by CALPUFF and the user must select an appropriate background concentration. The IWAQM Phase II Recommendations suggest typical ammonia concentrations as: 10 parts per billion (ppb) for grasslands, 0.5 ppb for forests,

9 USEPA Memorandum. Clarification on EPA-FLM Recommended Settings for CALMET. August 2009.

http://www.epa.gov/ttn/scram/CALMET%20CLARIFICATION.pdf 10 USEPA website containing PM speciation for source categories: http://www.epa.gov/ttn/chief/emch/speciation.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-24



### and 1 ppb for arid lands during warmer weather. Given the low background concentration over the Gulf of Mexico and as requested by the FLM, ENVIRON used a background ammonia concentration of 3 ppb. Reaction rates in the CALPUFF chemistry algorithms are also influenced by background ozone concentrations. ENVIRON used hourly ozone data for 2001-2003 to represent background ozone concentrations for the modeled years. This data was included in the VISTAS CALMET data. CALPUFF uses a background ozone value (BCK03) for hours when none of the supplied ozone stations have valid data. A conservative value of 65 ppb was specified, to avoid artificially limiting chemical transformations (e.g. NO X 

### titration). **6.4.6 Domain and Receptors** The domain for the CALPUFF simulations is shown in Figure 4. The 740 km-by-428 km domain is large enough to include the Class I areas of interest with at least a 50 km allowance for complex flows that might cause recirculation of plumes originating at the lease block Desoto Canyon (DC) 143. A Lambert Conformal Coordinate (LCC) system was used for the coordinates. The CALPUFF dispersion model simulations assessed AQRVs at discrete receptors obtained from the National Park Service 11 

### , and include elevations ranging from 0.021 to 0.375 m. Figure 4 also shows the discrete receptor locations within the Breton Class I area. Gridded receptors were turned off in the CALPUFF runs to make the runtimes more reasonable.

**6.4.7 Emission Rates and Stack Parameters** Modeled emission rates are discussed in Section 6.2.3 above. **6.4.8 Meteorological Data** Preprocessed VISTAS - BART 4 km Domain 2 CALMET data was used for modeling. This data was provided by the North Carolina Department of Environment and Natural Resources (NCDENR). Data from 109 surface stations, 10 upper air stations, 9 overwater stations and 96 precipitation stations was used to process the 2001 CALMET data. Data from 100 surface stations, 10 upper air stations, 9 overwater stations and 92 precipitation stations was used to process the 2002 CALMET data. Data from 116 surface stations, 10 upper air stations, 9 overwater stations and 103 precipitation stations was used to process the 2003 CALMET data. This is the most recent version developed by the FLM using the currently approved regulatory version of CALMET (Version 5.8). For the current analysis the 4-km mesh size simulations were used in order to better resolve the flow in the complex terrain. CALMET (Version 5.8), the meteorological preprocessor component of the CALPUFF system, was used to combine the MM5 simulation data, surface observations, terrain elevations, and land use data into the format required by the dispersion modeling component CALPUFF. In addition to specifying the three-dimensional wind field, CALMET also estimates the boundary layer parameters used to characterize diffusion and deposition by the dispersion model.

11 http://www.nature.nps.gov/air/maps/Receptors/index.cfmOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-25



### Selected hours of the three-year CALMET/MM5 three-dimensional data set were examined by extracting data from the CALMET output files and plotting the meteorological fields with the CALDESK software package. Wind vector plots were examined for different times of year, different times of day, and for all 10 vertical levels.
**6.4.9 AQRV Calculation Procedures** The CALPUFF modeling system was used to predict criteria pollutant concentrations, total deposition fluxes, and light extinction coefficients attributable to project emissions in regionalClass I areas. These parameters were calculated from CALPUFF output files using the postprocessor programs CALPOST and POSTUTIL.

Predictions of NO 2 

### and PM 2.5 

### concentrations in the Class I areas of interest were extracted from the annual and short-term emission cases using the CALPOST post-processor. Total nitrogen deposition fluxes are calculated by summing and converting the various species included in the wet and dry deposition CALPUFF output files. The nitrogen deposition fluxes include the nitrogen from the background ammonia to some extent. For comparison to FLM deposition criteria, the fluxes were converted to kilograms per hectare per year. **6.4.10 FLAG 2010 (CALPOST Method 8)** In order to provide further information, extinction coefficients were calculated using the 2010revisions to the FLM FLAG procedures. The revised procedures employ the IMPROVE extinction equation to calculate b ext 

### (invoked with MVISCHECK=1 in CALPOST). This updated equation for extinction uses monthly relatively humidity adjustment factors with relative humidity capped at 95%. It uses annual background aerosol concentrations recommended by the FLMs for the Class I area of concern, and assesses the visibility using the 98 th 

### percentile modeled values at each receptor. In order to use Method 8, CALPOST Version 6.221 (Level 080724) was used to post-process the CALPUFF output files. For FLAG 2010, a Project’s extinction is calculated using the revised IMPROVE reconstructed mass extinction equation as follows:

b project 

### = 2.2 × f S 

### (RH) × [Small Sulfate] + 4.8 × f L 

### (RH) × [Large Sulfate] + 2.4 × f S 

### (RH) × [Small Nitrate] + 5.1 × f L 

### (RH) × [Large Nitrate] + 2.8 × [Small Organic Mass] + 6.1 × [Large Organic Mass] + 10 × [Elemental Carbon] + 1 × [Fine Soil] + 0.6 × [Coarse Mass] + 1.7 × f SS 

### (RH) × [Sea Salt] + Rayleigh Scattering (Site Specific) + 0.33 × [NO 2 

### (ppb)] {or as: 0.1755 × [NO 2 

### (μg/m 3 

### )]} Where: [ ] indicates concentrations in μg/m 3 

### f S 

### (RH) = Relative humidity adjustment factor for small sulfate and nitrate f L 

### (RH) = Relative humidity adjustment factor for large sulfate and nitrate f SS 

### (RH) = Relative humidity adjustment factor for sea salt For Total Sulfate < 20 μg/m 3 

### : [Large Sulfate] = ([Total Sulfate] / 20 μg/m 3 

### ) × [Total Sulfate] For Total Sulfate ≥ 20 μg/m 3 

### :Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-26 

### [Large Sulfate] = [Total Sulfate] And: [Small Sulfate] = [Total Sulfate] – [Large Sulfate] To calculate large and small nitrate and organic mass, substitute ({Large, Small, Total} {Nitrate, Organic Mass}) for Sulfate. **6.4.11 Analysis Results** The CALPUFF modeling system was used to predict concentrations of NO 2 

### and PM 2.5 

### in the Class I area of interest. Table 6.4.11-1 summarizes the predicted maximum NO 2 

### and PM 2.5 

### concentrations and compares them to the Class I SILs. At this point, there are two sets of Class I SILs: those proposed by EPA, and those recommended by the FLMs. These proposed and recommended SILs were obtained from the Federal Register, Vol. 61, No. 143, p. 38292, July 23, 1996. As shown in Table 6.4.11-1, the CALPUFF simulations indicate neither the SILs nor the increments will be exceeded.

**Table 6.4.11-1 Maximum Predicted Class I Concentrations** 

**Criteria Pollutant Averaging Period**  **Developer Max.**  **Concentration (μg/m**  **3 )**  **Discoverer Americas** 

**Max. Concentration**  **(μg/m 3**  **) EPA SIL**  **(μg/m 3**  **) FLM SIL**  **(μg/m 3**  **)**

NO 2 a Annual 0.02 0.02 0.1 0.03

PM 2.5 b 24-hr 0.04 0.04 0.07 -- Annual 0.0004 0.0004 0.06 c -- Notes:

a NO X was conservatively assumed to be 75 percent converted to NO 2 . b 100 th percentile (maximum) values are presented (not 98 th percentile) using direct PM 2.5 emissions only.

c The Class I PM 2.5 SIL was vacated on January 22, 2013,but presented here for comparison. 

### CALPUFF was also used to predict the impacts of acid-forming compounds emitted by the project on soils and vegetation in the Class I area of interest. The deposition analysis results are shown in Table 6.4.11-2. The National Park Service (NPS) has established Deposition Analysis Threshold (DAT) for nitrogen of 0.010 kg/ha/yr for Class I areas to the east of the Mississippi river. 12 

### These “thresholds” are based on natural background deposition estimates culled from various research efforts, a variability factor, and a safety factor that accounts for cumulative effects. The DATs are not adverse impact thresholds, but are intended as conservative screening criteria that allow the FLMs to identify potential deposition fluxes that require their consideration on a case-by-case basis. As shown in Table 6.4.11-2, predicted maximum nitrogen deposition fluxes do not exceed the DATs.

**Table 6.4. 11** 
**- 2**  **Predicted Class I Area Deposition Fluxes**

12 Guidance on Nitrogen and Sulfur Deposition Analysis Thresholds, available on the FLAG internet site at

http://www2.nature.nps.gov/ard/flagfree/NSDATGuidance.htmOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-27 **Developer Discoverer Americas**  **Class I Area of Interest Nitrogen Deposition**  **Nitrogen Deposition** Breton Wilderness 0.0013 0.0014 NPS DAT 0.010 0.010 

### Comparison with FLM-recommended criteria for regional visibility impacts is shown by calculating the change in 24-hour extinction for each Class I receptor. The FLMs recommend in the FLAG Phase I Report that a five percent change in extinction be used to indicate a “just perceptible” change to a landscape. The CALPUFF modeling system was used to predict both the extinction coefficient attributable to emissions from the project as well as the background extinction coefficients for that day’s meteorology. As is required, all days with more than five percent change in extinction are disclosed. As shown in Tables 6.4.11-3 and 6.4.11-4, and summarized in Table 6.4.11-5, the 98 th 

### percentile predicted change in extinction at Breton Wilderness using Method 8 was less than 5 percent for two of the three years, for both the Developer and the Discoverer Americas emissions scenario. These results are less than the ten percent threshold established by the FLMs, which would cause the FLMs to be likely to object to the issuance of the permit. The FLMs should take into consideration the conservative nature of the modeling, and the relatively low extinction values for the single year that exceeds five percent. Conservative assumptions include:

 24-hour average emission rates were assumed to equal 1-hour maximum emission rates

 1-hour maximum emission rates were taken from the worst-case possible hour, with all equipment operating at 100% load, even emission units that in reality operate just a few hours per month.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-28 

### Table 6.4.11-3 **Predicted Extinction Change for Breton Wilderness, Method 8, Maersk**

**Date b**  **ext a**  **(1/Mm) Change**  **b ext**  **by Component c**  **(1/Mm) Project**  **Bckgrnd b**  **Total (%)**  **SO 4**  **NO 3**  **OC EC**  **PMC PMF**  **NO 2**  12/08/01 3.625 23.365 26.99 15.51 0.009 3.369 0.019 0.182 0 0 0.046 02/28/01 2.276 23.114 25.39 9.85 0.006 2.107 0.01 0.101 0 0 0.052 02/19/03 2.266 23.114 25.38 9.8 0.006 2.058 0.014 0.139 0 0 0.048 11/22/03 2.065 23.235 25.3 8.89 0.008 1.844 0.018 0.176 0 0 0.019 02/27/01 1.808 23.114 24.922 7.82 0.004 1.715 0.007 0.071 0 0 0.011 03/16/03 1.702 23.085 24.787 7.37 0.003 1.612 0.007 0.068 0 0 0.012 02/21/01 1.679 23.114 24.793 7.26 0.003 1.539 0.007 0.072 0 0 0.057 05/01/03 1.636 23.246 24.882 7.04 0.006 1.499 0.011 0.11 0 0 0.01 04/05/01 1.61 23.042 24.651 6.99 0.006 1.357 0.015 0.146 0 0 0.086 02/20/01 1.498 23.114 24.613 6.48 0.004 1.35 0.009 0.09 0 0 0.046 11/20/02 1.482 23.235 24.717 6.38 0.002 1.401 0.005 0.048 0 0 0.026 01/28/02 1.418 23.376 24.794 6.07 0.004 1.287 0.009 0.083 0 0 0.035 02/20/03 1.341 23.114 24.455 5.8 0.003 1.208 0.008 0.073 0 0 0.048 12/07/01 1.324 23.365 24.689 5.67 0.003 1.223 0.007 0.066 0 0 0.024 09/17/01 1.176 23.493 24.67 5.01 0.011 0.932 0.021 0.204 0 0 0.009 Notes:

a Project and background extinction values for daily period that resulted in the maximum percent change in extinction.
b Background extinction derived from default annual average extinction components provided in FLAG 2010 Tables.

c Extinction coefficient components are: SO 4 = fine sulfate, NO 3 = fine nitrate, OC = fine organic carbon, EC = fine elemental carbon, PMC = coarse mass, PMF = fine crustal mass, NO 2 = nitrogen dioxide.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-29 

### Table 6.4.11-4 **Predicted Extinction Change for Breton Wilderness, Method 8, Transocean**

**Date b**  **ext a**  **(1/Mm) Change**  **b ext**  **by Component c**  **(1/Mm) Project**  **Bckgrnd b**  **Total (%)**  **SO 4**  **NO 3**  **OC EC**  **PMC PMF**  **NO 2**  12/08/01 5.112 23.365 28.477 21.88 0.011 4.799 0.022 0.216 0 0 0.064 02/28/01 3.254 23.114 26.368 14.08 0.007 3.04 0.013 0.122 0 0 0.073 02/19/03 3.194 23.114 26.308 13.82 0.008 2.938 0.017 0.165 0 0 0.067 11/22/03 2.999 23.235 26.234 12.91 0.01 2.734 0.021 0.209 0 0 0.025 02/27/01 2.621 23.114 25.735 11.34 0.005 2.507 0.009 0.085 0 0 0.016 03/16/03 2.474 23.085 25.559 10.72 0.004 2.366 0.008 0.079 0 0 0.017 02/21/01 2.39 23.114 25.504 10.34 0.004 2.209 0.009 0.086 0 0 0.083 05/01/03 2.331 23.246 25.577 10.03 0.007 2.167 0.013 0.13 0 0 0.014 04/05/01 2.299 23.042 25.34 9.98 0.007 1.975 0.018 0.175 0 0 0.123 02/20/01 2.193 23.114 25.307 9.49 0.005 2.004 0.011 0.107 0 0 0.066 11/20/02 2.125 23.235 25.36 9.15 0.003 2.025 0.006 0.056 0 0 0.035 01/28/02 2.049 23.376 25.426 8.77 0.005 1.882 0.01 0.1 0 0 0.052 02/20/03 1.993 23.114 25.107 8.62 0.004 1.819 0.009 0.09 0 0 0.071 12/07/01 1.843 23.365 25.208 7.89 0.004 1.719 0.008 0.078 0 0 0.034 09/17/01 1.689 23.493 25.182 7.19 0.013 1.395 0.025 0.244 0 0 0.013 04/13/02 1.599 23.042 24.64 6.94 0.002 1.552 0.004 0.035 0 0 0.006 01/29/02 1.445 23.376 24.822 6.18 0.005 1.231 0.01 0.102 0 0 0.097 05/26/02 1.424 23.246 24.67 6.13 0.004 1.32 0.008 0.081 0 0 0.011 07/08/03 1.384 23.733 25.117 5.83 0.008 1.123 0.016 0.157 0 0 0.08 01/17/02 1.354 23.376 24.731 5.79 0.003 1.28 0.006 0.061 0 0 0.004 11/26/03 1.277 23.235 24.513 5.5 0.004 1.127 0.01 0.102 0 0 0.033 02/25/02 1.267 23.114 24.381 5.48 0.003 1.152 0.008 0.075 0 0 0.028 03/11/01 1.251 23.085 24.336 5.42 0.002 1.149 0.006 0.058 0 0 0.036 04/24/01 1.229 23.042 24.271 5.33 0.003 1.086 0.008 0.077 0 0 0.055 05/02/03 1.179 23.246 24.424 5.07 0.003 1.101 0.006 0.057 0 0 0.011 09/30/02 1.189 23.493 24.682 5.06 0.006 1.042 0.012 0.116 0 0 0.014 10/09/02 1.162 23.221 24.383 5 0.007 0.919 0.015 0.149 0 0 0.072 Notes:

a Project and background extinction values for daily period that resulted in the maximum percent change in extinction.
b Background extinction derived from default annual average extinction components provided in FLAG 2010 Tables.

c Extinction coefficient components are: SO 4 = fine sulfate, NO 3 = fine nitrate, OC = fine organic carbon, EC = fine elemental carbon, PMC = coarse mass, PMF = fine crustal mass, NO 2 = nitrogen dioxide.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-30 

### Table 6.4.11-5 **Maximum Predicted Extinction Change for Breton Wilderness, Method**  **8 Summary Criteria**  **Developer Discoverer Americas**  Highest Value 15.51 21.88 Number Days > 5% change 15 27 Number Days > 10% change 1 8 98 th Percentile Change, 2001 5.01 7.19 98 th Percentile Change, 2002 3.51 5.06 98 th Percentile Change, 2003 3.69 5.07 

## 6.5 **Additional Impacts Assessment** An additional impacts analysis was performed in accordance with PSD requirements (40 CFR 52.21(o)). The analysis evaluates the potential impacts that the proposed Statoil exploration activities could have on growth, soils, vegetation, and visibility in the area surrounding the proposed drilling locations. **6.5.1 Growth Analysis** Statoil examined the potential growth in industrial, commercial and residential sources as a result of the proposed DeSoto Canyon and Lloyd Ridge drilling exploration activities and determined that no growth is expected. This determination was reached based on Statoil’s deep understanding of the robust and well developed oil and gas industry that currently supports exploration activities in the area just west of the proposed drilling activities. It is expected that the current infrastructure is more than adequate to support the proposed drilling activities and thus no growth is expected. **6.5.2 Soil and Vegetation Impacts** The PSD draft guidelines prescribe that the potential impacts of the proposed project on the soils and vegetation in the vicinity of the facility should be considered. As approved in the modeling protocol, due to the location of the proposed exploration activities in the eastern Gulf of Mexico, no impact to local soils or vegetation is expected. **6.5.3 Local Visibility Impairment** Local visibility analysis was conducted using the EPA plume impact screening model (VISCREEN, version 1.01). VISCREEN calculates the potential visual impact of a plume of specified emissions for specific transport and dispersion conditions. A VISCREEN Level I analysis was conducted to estimate if the proposed exploration activities could result in an adverse impact on visibility for the closest Class II area receptor. The closest Class II area receptor to the lease block in the Gulf of Mexico was located on the edge of the Mississippi Delta, over 50km away. To maintain a conservative analysis, and because VISCREEN is not applicable beyond 50km, 50km was used as the source to class I area distance. Level I analysis utilizes particulate matter and NO x 

### emission rates as inputs, while using default values for background ozone, stability class and wind speed. The default background ozone concentration is 0.04 ppm, while default stability and wind speed are 6 and 1 m/s, respectively.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-31



### The model conservatively evaluates whether a plume from Developer or Discoverer Americas drilling vessels and associated support vessels is perceptible to an observer under worst case meteorological conditions from a known distance. Several angles between the observer’s line of sight and the sun’s radiation (θ) are considered. The input emission rates for Developer or Discoverer Americas drilling vessels and associated support vessels are listed in Tables 6.5.3-1 and 6.5.3-2. The default input parameters are listed in Table 6.5.3-3.

**Table 6.5.3-1 Level I**  **Developer VISCREEN Analysis Input Parameters**  **Developer Short-Term Emission Rates**  **Emissions (lb/hr)** Particulate Matter 13.82 NOx (as NO 2 ) 579.32 Primary NO 2 0 (default) Soot 0 (default) Primary SO 4 0 (default)



### Table 6.5.3-2 **Level I Discoverer Americas**  **VISCREEN Analysis Input Parameters Discoverer Americas**  **Short-Term Emission Rates Emissions (lb/hr)**  Particulate Matter 16.55 NOx (as NO 2 ) 818.68 Primary NO 2 0 (default) Soot 0 (default) Primary SO 4 0 (default)



### Table 6.5.3-3 **Level I Developer**  **and Discoverer Americas**  **VISCREEN Analysis Input Parameters Input Parameters**  Background Ozone (ppm) 0.04 Background Visual Range (km) 20 Distance: Source to Closest Class I Area (km) 50 Distance: Source to Farthest Class I Area (km) 50 Source-Observer Distance (km) 50 Plume-Source-Observer Angle 11.25 Stability 6.0 Wind Speed (m/s) 1.0 

### The VISCREEN model is designed to determine whether the plume from an emission source has the potential to be traceable to an untrained observer under reasonable worst case conditions. Two screening criteria are used to carry out the analysis and if either criterion is exceeded, more comprehensive analyses should be carried out. The first criterion, delta E, known as the plume perceptibility parameter is based on the difference in color and brightnessOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-32



### between the plume and the background. It is also known as the color difference parameter and depends on three factors, namely, brightness (L), color hue (a) and color saturation (b).
Mathematically,
ΔE = [(ΔL) 2 

### + (Δa) 2 

### + (Δb) 2 

### ] 1/2



### The default threshold for delta E is 2.0
The second criterion is called the green contrast value (C plume or 

### C p 

### ). C p 

### is defined as the contrast of a plume against a viewing background such as the sky or a terrain feature. Change is measured in terms of green color (wavelength=0.55 microns). The default threshold for C p 

### is 0.05. Level I screening results are listed in Table 6.5.3-4 and Table 6.5.3-5.

**Table 6.5.3-4 Level I**  **Developer VISCREEN Results** 

**Background θ**  **Distance (Source-Observer) (km)**  **Delta E Contrast**  **Critical Plume**  **Critical Plume**  Sky 10 50 2.00 1.088 0.05 -0.006 Sky 140 50 2.00 0.337 0.05 -0.007 Terrain 10 50 2.00 0.087 0.05 0.001 Terrain 140 50 2.00 0.026 0.05 0.001



### Table 6.5.3-5 **Level I Discoverer Americas**  **VISCREEN Results**

**Background θ**  **Distance (Source-Observer) (km)**  **Delta E Contrast**  **Critical Plume**  **Critical Plume**  Sky 10 50 2.00 1.449 0.05 -0.008 Sky 140 50 2.00 0.449 0.05 -0.010 Terrain 10 50 2.00 0.118 0.05 0.002 Terrain 140 50 2.00 0.036 0.05 0.002



### As listed in Table 6.5.3-4 and Table 6.5.3-5 above the default threshold for delta E and Cp was not exceeded for both sky and terrain backgrounds for either Developer or Discoverer Americas ; therefore, the proposed exploration activities are not expected to impair the local visibility. VISCREEN modeling outputs are included with this air quality impact analysis.

**6.5.4 Ozone Assessment** As documented in the analysis below, Statoil has concluded that the proposed exploratory drilling activities will not significantly impact the current ozone levels in the eastern Gulf of Mexico. This conclusion is based on the relatively low quantity of project emissions, the distance needed to travel to impact ground-level ozone and the frequent wind direction changes.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-33



### 6.5.4.1 Ozone Formation Ozone is an air pollutant formed through complex chemical reactions of nitrogen oxide (NO x 

### ) and volatile organic compound (VOC) emissions, during periods of conducive weather conditions. Ozone is more readily formed when it is sunny and hot and the air is stagnant. Conversely, ozone production is more limited when it is cloudy, cool, rainy, and windy. For these reasons, ozone concentrations are generally the highest during the summer. The majority of tropospheric ozone formation occurs when nitrogen oxides (NO x 

### ), carbon monoxide (CO) and volatile organic compounds (VOCs) react in the atmosphere in the presence of sunlight. NO x 

### , CO, and VOCs are called ozone precursors. The chemical reactions involved in tropospheric ozone formation are a series of complex cycles in which carbon monoxide and VOCs are oxidized to water vapor and carbon dioxide. The reactions involved in this process are illustrated below with CO but similar reactions occur for VOC as well. Oxidation begins with the reaction of CO with the hydroxyl radical. The hydrogen atom formed by this reacts rapidly with oxygen to give a peroxy radical HO 2 

### OH + CO → H + CO 2 

### H + O 2 

### → HO 2 

### Peroxy radicals then go on to react with NO to give NO 2 

### , which is photolysed (indicated by hν) to give atomic oxygen and through reaction with oxygen a molecule of ozone:

HO 2 

### + NO → OH + NO 2 

### NO 2 

### + hν → NO + O O + O 2 

### → O 3 

### The net effect of these reactions is:

CO + 2O 2 

### → CO 2 

### + O 3 

### This cycle involving HO x 

### and NO x 

### is terminated by the reaction of OH with NO 2 

### to form nitric acid or by the reaction of peroxy radicals with each other to form peroxides. The chemistry involving VOCs is much more complex but the same reaction of peroxy radicals oxidizing NO to NO 2 

### is the critical step leading to ozone formation. **6.5.4.2 Project Emissions Relative to Existing Emissions** For this project, the estimated annual emissions for NO x 

### and VOCs are shown in Table 6.5.4.2- 1, for the Maersk Developer and Transocean Discoverer Americas . The estimated emissions include the contributions from the support fleet, including crew boats, and supply vessels. Because the sum of NO x 

### emissions exceeds 100 tons per year, an assessment of the project’s potential effects on regional ozone concentrations is required. According to the information presented in the Oil and Gas Exploration section on the NOAA Ocean Explorer website 13 

### there are 3,858 oil rigs or platforms in the Western and Central Planning Areas of the Gulf of Mexico (GOM). The locations of these oil rigs and platforms are

13 

### http://oceanexplorer.noaa.gov/explorations/06mexico/background/oil/oil.htmlOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-34



### shown in Figure 4. Figure 4 also illustrates the Statoil lease block locations in relation to the current oil and gas well locations in the GOM.Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-35Outer Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-36 

### Further analysis based on the 2008 Emissions Inventory from the Bureau of Safety and Environmental Enforcement (BSEE) showed that some of these rigs or platforms are either inactive, weren’t included in the emissions inventory report, or have been decommissioned. In 2008 there were 3,027 point sources emitted either VOC or NO x 

### and were located west of the 87 degree 30 minute Longitude. The emissions data found in the BOEMRE 2008 Gulfwide Emission Inventory Study Report 14 

### (the latest finalized inventory) is summarized in Table 6.5.4.2-1, for comparison with Statoil’s estimated potential annual emissions.

**Table 6.5.4.2-1 2008 Emissions of NOx and VOCs from Point Sources in the Gulf of Mexico** 
**Pollutant Source**  **Emissions (TPY)** NOX Maersk Developer 484 VOC Maersk Developer 28 NOX Transocean Discoverer Americas 560 VOC Transocean Discoverer Americas 25 NOX 1,388 Existing Emission Points 74,286 VOC 3,026 Existing Emission Points 60,824



### When compared with the total emission amounts for NO x 

### and VOCs from all the sources in Gulf of Mexico, the proposed project emissions will at most account for 0.8% of total NO x 

### and 0.05% of total VOC emissions, respectively. Table 6.5.4.2-2 presents the statewide total NO x 

### emissions from the 2008 National Emissions Inventory (NEI) 15 

### for the States around the Gulf of Mexico. The total NO x 

### emissions for these States are summarized based on the information in the Technical Support Document (TSD) for the EPA Federal Transportation Rule (TR) (EPA-HQ-OAR-2009-0491). The TSD also showed that the on-road sources contributed 36% to the total NO x 

### emissions in the Gulf States. Estimated project emissions are very small compared with the total NO x 

### emissions of nearly 4.0 million tons from the five states in the region.

14 

### http://www.bsee.gov/Environmental-Stewardship/Environmental-Studies/Gulf-of-Mexico-Region/AirQuality/2008-Gulfwide-Emission-Inventory.aspx 15 

### http://www.epa.gov/ttnchie1/net/2008inventory.htmlOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-37 

### Table 6.5.4.2-2 **State - Level Total NO x**  

### Emissions for Gulf States in the 2008 NEI **State NO**  **x Emissions (TPY)**  Alabama 421,467 Florida 895,436 Louisiana 548,439 Mississippi 278,745 Texas 1,827,200 **Total 3,971,287** 

### Ozone concentrations measured at the sites shown in Figure 5 are much more likely to be the result of the vast quantity of NO x 

### and VOC emissions from existing mobile (traffic) and onshore point (e.g. refineries) sources, rather than from the much smaller emissions associated with the project.

Figure 5. Ozone Monitors closest to the Statoil Lease Blocks In addition, the Statoil lease block closest to shore is more than 150 km (93 miles) from the nearest coastline at the mouth of the Mississippi Delta. As such, the project’s NO x 

### and VOCemissions will need to travel more than 100 miles to reach the coastline to contribute to onshore ozone concentrations. Furthermore, as shown in Figure 6, the wind speed and directionOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-38



### in the EGOM frequently changes; as such, the emissions from this project will be dispersed over a wide area.

Figure 6 Wind Rose of EGOM Weather Buoy (WMO #995000) 16

16 

### WRPLOT View – Lakes Environmental SoftwareOuter Continental Shelf PSD/Title V Permit Application

Air Quality Impact Assessment 6-39



### Based on the above analysis and with the consideration of:

 The total number of oil rigs and platforms in the Western Gulf of Mexico and the total emissions of NO x 

### and VOCs from these existing sources;

 The distance between the Statoil lease blocks and the nearest coastline;

 Total NO x 

### emissions from the States around the Gulf of Mexico; and,

 Frequent wind direction change and atmospheric disturbances in the Gulf of Mexico; We do not expect project emissions to impact ozone formation on the coastal areas around the Gulf of Mexico.